There are various ideas on this, Ian. I keep mine in their pots, but allow them to dry out and keep them in a dry, frost-free (but cool) light place (porch/loft/greenhouse/conservatory). I have heard that you can knock the soil off their roots, wrap them in newspaper and leave them in a cool room, either under the spare bed on top of the wardrobe. I think you need to cut them back quite a lot in the autumn, but I have seen neighbours here who don't bother, and stow them away still with all their summer growth on. Come spring, cut off any bits that have died, bring out into the warm spring air, repot and take cuttings from the new shoots that will begin to grow, and start to water them.

Yes I keep mine indoors and now are starting to bloom once again .

Outdoors no way in winter.

Also, they won't survive in an unheated greenhouse. Keep them on the dry side and only water sparingly during mild spells. They will put up with the cold better if kept dryer.

I group all mine together on the balcony, still with their remaining flowers. Come Spring, remove old flower stems and some old growth, re-pot, water and away they go. The only extra measure I sometimes take is to swathe them over with fleece or bubble wrap if extra cold weather is forecast. This method has worked for six years.

How cold do your winters get, Nariz?

Well .... brass monkeys spring to mind, Gattina. Being 700 masl means we get the freezing howling winds that funnel down the valley from the higher peaks and obviously we get the snow when the folk in the valley are still blissfully unaware. A good measure of how cold it gets is to measure the distance between our settee and the log fire. At present the distance is about 8' but - if Spanish weather predictions are right (and they're often way off!) - it's about to creep in to about 6' !!

Much like us (she says, peering out of the window at 60cms snow and whirling flakes and broken branches) then! Last winter we put our pelargoniums up in the loft under a nice bright skylight, and, thanks to all the loft insulation, most of them froze anyway :o( (well, it DID get down to -22°c outside)
How dry do you let yours get? I suppose (speaking as a complete ignoramus here) leaving them in the light means they do need a little bit of dampness at the roots, whereas if they are going to be kept in the dark, they can be allowed to dry out almost completely. Is that right?
p.s. sofa and armchairs still at about 8' from stove. Thank goodness for firewood and candles in a blackout!

Yes, I water my pelargoniums a little occasionally - nothing like the quantities they receive during the growing season. Not sure about storing in the dark as I've never done it.